1. Field of Invention
The present invention relates to an electro-optical panel, an electro-optical panel module, and a projection display device, and, more particularly, to an electro-optical panel structure suitable for use as a light valve of the projection display device.
2. Description of Related Art
An electro-optical panel for performing light modulation to form a predetermined image is sometimes used in a projection display device such as a liquid crystal projector. Here, a condensing optical system and an enlarging projection optical system are provided. The condensing optical system is provided to cause light from a light source to strike the electro-optical panel. The enlarging projection optical system is provided to project the light that has passed through the electro-optical panel onto a projection surface, such as a screen, and form an enlarged image. The light condensed by the condensing optical system passes through the electro-optical panel, resulting in the formation of the predetermined image, which is projected towards the front by the enlarging projection optical system.
However, when dust sticks onto the outer surface of two transparent substrates making up the above-described electro-optical panel or when the outer surface of the two transparent substrates get scratched, the outer surface of the transparent substrates are brought to a focus, since the outer surface of the transparent substrates are separated from a liquid crystal layer of the electro-optical panel that is brought to a focus by the condensing optical system by only about 1 mm. Therefore, the above described electro-optical panel has the problem that the quality of a projected image is considerably reduced even when the dust or scratches which get enlarged and projected are only about 10 xcexcm to 20 xcexcm in size.
In the projection display device, the electro-optical panel is irradiated with intense light generated from a light source, so that a localized temperature rise tends to occur in the electro-optical panel. Since such temperature rise changes the light transmittance ratio of some liquid crystals, display quality is reduced. In addition, such temperature rise causes deterioration in electro-optical substances such as the aforementioned liquid crystals.
In view of these problems, Japanese Unexamined Patent Publication Nos. 9-105901 and 9-113906 disclose a technology which increases heat dissipating capability and which prevents dust from sticking onto and scratches from being formed on the outer surface of a transparent substrate of an electro-optical panel. In this technology, another transparent substrate is disposed away from the aforementioned transparent substrate of the electro-optical panel, with an adhesive being used and applied to the outer surface of the transparent substrate of the electro-optical panel. When another transparent substrate is disposed, an air gap is formed between the transparent substrates separated from each other, so that heat dissipating capability is increased. In addition, when another transparent substrate is disposed, it is possible to prevent dust from sticking onto and scratches from being formed on the outer surface of the transparent substrate of the electro-optical panel. However, when this technology is used, another transparent substrate is disposed away from the transparent substrate of the electro-optical panel, so that light is reflected at the interface between the electro-optical panel and the air gap and at the interface between the transparent substrate disposed away from the transparent substrate of the electro-optical panel and the air gap. This results in such problems as loss of a large amount of light, and the necessity of performing an additional step to form a reflection prevention film onto the substrate surfaces in order to prevent reflection of light.
In order to overcome the above-described problems, the present inventor has conducted various studies on methods of adhering a surface of another substrate onto the outer surface of a transparent substrate of an electro-optical panel, using a transparent adhesive. An application of a method based on such studies has already been filed. FIG. 6 is a schematic view of the structure of an electro-optical panel based on this method. In the electro-optical panel, liquid crystals, which are electro-optical substances, are filled and sealed with a sealant (not shown) between an element-formed substrate 11 (having a pixel electrode and an active element formed on the inner surface thereof) and an opposite substrate 12 (having an electrode that opposes the pixel electrode and that is formed on the inner surface thereof) that opposes the element-formed substrate 11. A surface of a transparent substrate 28 is adhered to the outer surface of the element-formed substrate 11 with a transparent adhesive 30, while a surface of a transparent substrate 29 is adhered to the outer surface of the opposite substrate 12 with a transparent adhesive 30. However, when this method is used, the transparent adhesives 30 do not allow flexing of the electro-optical panel, and must have refractive indices of light which are substantially the same as those of the element-formed substrate 11, the opposite substrate 12, and the transparent substrates 28 and 29, so that there is a limit as to the kind of adhesive material which can be used. The adhesive material used must have low viscosity and must possess flowing properties to a certain extent after it has hardened. Therefore, as shown in FIG. 6, after the surfaces of the corresponding substrates have been adhered together, the transparent adhesives 30 flow outwardly from adhesion portions between the corresponding substrates. Consequently, during the manufacturing process or after completion of the manufacturing process, it becomes difficult to handle the electro-optical panel. In addition, since the transparent adhesives 30 tend to accidentally stick onto the outer surface of the transparent substrates 28 and 29, the electro-optical panel produced tends to be defective.
To overcome the above-described problems, it is an object of the present invention provides a novel structure which makes it possible to facilitate handling of electro-optical panels and to reduce the number of defective electro-optical panels as a result of reducing the amount of transparent adhesive overflowing from the electro-optical panels by changing the form of a transparent substrate, in the case where a surface of another transparent substrate is adhered to the outer surface of a transparent substrate of the electro-optical panels with transparent adhesives.
To this end, according to a first aspect of the present invention, there is provided an electro-optical panel which includes: a first substrate, a second substrate, an electro-optical substance sandwiched between an inside surface of the first substrate and an inside surface of the second substrate, a third substrate bonded at an outer side of at least one of the first substrate and the second substrate with an adhesive, and a stepped portion formed by disposing an end surface of the first substrate and an end surface of the third substrate out of line with respect to each other, with the first substrate and the third substrate opposing each other with the adhesive being disposed therebetween.
In such a structure, even when scratches are formed on or dust sticks onto the outer surface of the first substrate, the dust or scratches separate from the electro-optical substance and defocusing occurs when a surface of the third substrate is adhered to, for example, the first substrate. Therefore, it is possible to prevent the display quality from being reduced; to increase the heat capacity of the electro-optical panel; and to reduce the extent to which the display quality is deteriorated by overheating of the electro-optical substance. In addition, when a stepped portion is formed by an end surface of the first substrate and an end surface of the third substrate (with an adhesion portion being formed therebetween), any adhesive which flows from the transparent substrates is collected and retained by the stepped portion as long as the amount of adhesive which flows from between the transparent substrates falls within a certain range, thus preventing adhesives from flowing outwardly of the stepped portion. Therefore, during the manufacturing process or after the manufacturing process, it is possible to eliminate the problem of difficulty in handling the electro-optical panel caused by an adhesive sticking onto an outer surface of the electro-optical panel, or the production of a defective product caused by an adhesive sticking onto a light-transmissive portion of the electro-optical panel. Further, since the adhesive hardens while it is collected at the stepped portion, the first substrate and the third substrate can be adhered more strongly together.
The stepped portion may be formed by forming the first substrate and the third substrate with different sizes as viewed in a plane.
In such a structure, a stepped portion can be formed by simply changing the size of the first substrate and the third substrate, making it unnecessary to perform special processing operations on the end surfaces of the substrates.
When the stepped portion is formed by forming the first substrate and the third substrate with different sizes as viewed in a plane, the third substrate may be larger than the first substrate, with an end surface of the first substrate being disposed inwardly of an end surface of the third substrate.
In such a structure, an end surface of the first substrate is disposed inwardly of an end surface of the third substrate. In other words, the third substrate is formed larger than the first substrate so as to extend beyond it. Therefore, even if any adhesive flows out of the electro-optical panel, the amount of adhesive flowing out of the electro-optical panel can be reduced, since the third substrate is formed so as to cover the first substrate.
According to a second aspect of the present invention, there is provided an electro-optical panel including: a first substrate, a second substrate, an electro-optical substance sandwiched between an inner side of the first substrate and an inner side of the second substrate, a third substrate adhered to an outer surface of the first substrate with an adhesive, and a groove formed in a peripheral portion of a surface of at least one of the first substrate and the third substrate where the adhesive is applied.
In such a structure, even if any adhesive overflows from the substrates, the overflown adhesive can be collected and retained by the stepped portion as long as the amount of adhesive that has overflown from the substrates falls within a certain range. Thus, the overflown adhesive can be prevented from flowing out of the groove. Consequently, during the manufacturing process or after the manufacturing process, it is possible to eliminate the problem of difficulty in handling the electro-optical panel caused by an adhesive sticking onto an outer surface of the electro-optical panel. In addition, since the adhesive hardens while it is collected in the groove, the first substrate and the third substrate can be adhered together more strongly.
The end surface of at least one of the first substrate and the third substrate may have an inclined surface portion which inclines towards an inner side of the substrate with the inclined surface portion.
In such a structure, an inclined surface portion is formed on an end surface of at least one of the first substrate and the third substrate, so that a wider area for collecting the overflowing adhesive can be provided. Therefore, it is possible to prevent the adhesive from flowing out of the electro-optical panel.
The inclined surface portion may be formed on a portion of the end surface at the adhesive-applied side of at least one of the first substrate and the third substrate in a direction of thickness thereof.
In such a structure, the inclined surface portion allows any adhesive which has overflown from the substrates to be collected there. In addition, since the inclined surface portion is formed on a portion of the end surface at the adhesive-applied side of at least one of the first substrate and the third substrate, the remaining portion of the end surface where the inclined surface portion is not formed can be formed perpendicular to a plane of the first substrate or the third substrate as is ordinarily the case, so that the electro-optical panel can be gripped by the end surface and positioned using the end surface.
The stepped portion may be formed by positioning the first substrate and the third substrate out of line with respect to each other in a direction in a plane, and adhering their surfaces together.
In such a structure, since a stepped portion can be formed by an end surface of the first substrate and an end surface of the third substrate even when the third substrate is formed to a size equal to that of the first substrate, no special processing operations whatever need to be performed on the substrates.
The refractive index of light of the third substrate and that of the transparent adhesive may be substantially the same as the refractive index of light of the first substrate.
In such a structure, reflection of light at the interface between the transparent adhesive and the third transparent substrate can be reduced.
The transparent adhesive may be resilient after it has hardened.
In such a structure, the use of a transparent adhesive which is resilient even after it has hardened makes it possible to reduce distortion of the substrates caused by application of stress generated during hardening of the transparent adhesive.
The angle of penetration of the adhesive after it has hardened may be from 60 degrees to not more than 90 degrees.
In such a structure, it is possible to prevent distortion of the substrates by reducing the amount of transparent adhesive flowing from the substrates to a minimum and letting the transparent adhesive itself absorb the stress.
The adhesive may have a thickness of from 5 xcexcm to 30 xcexcm.
In such a structure, it is possible to hide the dust or scratches on the substrates by the adhesive by forming it to a thickness equal to or greater than 5 xcexcm. When the adhesive is formed to a thickness equal to or less than 10 xcexcm, the adhesive strength can be made sufficiently high.
According to a third aspect of the present invention, there is provided an electro-optical panel module including: any one of the above-described electro-optical panels, a wiring member connected to any one of the above-described electro-optical panels so as to allow electrical conduction, and a case member for accommodating any one of the above-described electro-optical panels therein.
In such a structure, it is possible to reduce the amount of adhesive flowing from the substrates by the case member.
According to a fourth aspect of the present invention, there is provided a projection display device including: any one of the above-described electro-optical panels, or the above-described electro-optical panel module used as a liquid crystal light valve.
The projection display device includes a condensing optical system for condensing light emitted from a light source at any one of the above-described electro-optical panels; and an enlarging projection optical system for enlarging and projecting the light that has passed through any one of the above-described electro-optical panels and that has been modulated thereby onto a projection surface, such as a screen.
The present invention is highly effective when it is applied, in particular, to a projection display device which is greatly affected by scratches or dust on the outer surface of a substrate of an electro-optical panel, and whose electro-optical panel tends to overheat.
According to another aspect of the present invention, there is provided an electro-optical panel comprising a first substrate, a second substrate adhered to the first substrate with a sealant, an electro-optical substance sandwiched between the first substrate and the second substrate, a third substrate disposed on the outer side of at least one of the first substrate and the second substrate, wherein, the size of the third substrate is larger than the size of the first substrate, and the position of the end surface of the first substrate is inner than that of the third substrate, and the shielding member is disposed on the third substrate, along the peripheral of the third substrate.
In the aforementioned structure, the external form of the third substrate is larger than that of the first substrate, and further, the light shielding member is disposed along the peripheral region of the third substrate. Thus, it is possible to block off the light which is going to obliquely enter the electro-optical panel.
Further, in the aforementioned structure, the incident light from the the third substrate side travels through the first substrate and then is emitted from the second substrate. The light shielding member is disposed so as to cover and extend outward over the sealant, as viewed in plane.
Still further, according to the aforementioned structure, the light shielding member extends outward over the sealant. Thus in the case that, for example, a thin film transistor is formed in the display area on the first substrate, it is possible to prevent the scattered light occurring at the sealant from entering into the thin film transistors or the like, thereby also preventing the deterioration of the thin film transistor characteristics.
According to another aspect of the present invention, the incident light from the third substrate side travels through the first substrate and then is emitted from the second substrate side. A shielding film is disposed on at least one of the first substrate and the second substrate so that the position of the shielding film is inner than that of the sealant. The shielding member overlaps with the shielding film as viewed in a plane, and extends outward over the sealant.
In the aforementioned structure, the shielding film, which is positioned inner than the sealant, and the shielding member overlap with each other, as viewed in a plane. Therefore, it is possible to block off the light generated around the display area and prevent the linkage of the light. As a result, the display images has high contract, and undesirable effects on the panel due to the light leakage and the deterioration of thin film transistor characteristics can be prevented.
According to the another aspect of the present invention, the light shielding member is disposed on a side of the third substrate facing the electro-optical substance.
In the aforementioned structure, the gap between the shielding film, which is provided on the inward side of the sealant, and the shielding member is smaller than the same in the case that the shielding member is provided on the other side of the third substrate, namely the side the opposite to the side facing the electro-optical substance. Therefore, the positioning of the light shielding film and the light shielding member is performed easily so as to overlap each other.
According to the another aspect of the present invention, the light shielding member is disposed on the rear side of the third substrate the other side of which faces the electro-optical substance.
In the aforementioned structure, the shielding member is disposed on the peripheral region of the third substrate. This structure is more effective in blocking off the light, which is going to enter the sealant obliquely.
According to another aspect of the present invention, the surface of the first substrate is adhered to the surface of the third substrate with adhesive.
In the aforementioned structure, air layer does not exist since the surfrace of the first substrate and the surface of the third substrate are adhered to each other with adhesive. Therefore, the light reflection generating at the interface between the panel and the air layer can be prevented. Further, according to the aforementioned structure, the third substrate, which is provided on the outer side of the first substrate, is larger than the first substrate. Accordingly, even if the adhesive flows out, the amount of adhesive flowing out of the electro-optical panel can be reduced.
It is to be noted that in the above-described electro-optical panels, it is preferable to adhere a surface of the third substrate to the outer surface of the second transparent substrate with a transparent adhesive, too.